Improvement in duplex telegraphs



`'.lY.A.E 1nrso1\r. DUPLEX TELEGRAPH.

No. 178,222. Patented May 30,1876.

MAIN LINE INDUCTION WIL 3. nessuna: U

MMN BATTERY GGGG ND GGGG ND Y cores, so that the armature UNITED STATES PATENT OFFICE..

NEWARK, NEW JERSEY, AssIGNoR oE 4ONE-HALE His RIGHT To GEORGE E. PREsooTT,

OF NEW YORK CITY.

.IMPROVEMENT |N DUPLEX 'r'El-.EGRAPl-ls.

Specification forming part of Letters Patent No. 178,222., dated May 30, 1876 application filed September 1,

In the accompanying diagram drawing, the battery a b is connected at an end to the linewire c, at the other` end to the closed key e, and in the middle to the ground. The connection 3, from the key e to the line c, passes through the induction-coil and core f, and there is a second inductioncoil, g, around the coil f, that is in a shunt between the lineconnection c and the branch 7L to the ground, in which branch h there is a resistance, 7c, that is adjustable.

The line-connection c bifurcates at i, ing one Waythrough the helix Z to the groundand the other Way through the helix m to the main line s. The electro-magnet Zm, being wound in the not respond when the connection is made in the'middle, because the current passing from c goes one way through one helix, and the other Way through the other, polarizingv the r is not attracted.

t is important that the resistance of the branch h and rheostat lc should the same as that of the main line s, so as to cause the current to divide equally at t'.

understood that station passing through the magnet m, in the usual direction,will cause the armature to respond, whether there is any current passing through the helices or not from the sending-station, and this electromagnet m and armature act as a relay to operate the local circuit s and sounder t. p

The main battery, it will be seen, is in a local circuit when the key e is closed; hence, if both sides are equal, there is no current passing upon the main line; but when the key e is open the local circuit is broken,

portion through Z returning to ct through the branch h and ground.

When the key e is closed the induction-coil f is charged, -and it discharges when the key e is opened. Thehelixg, that has been charged by induction, also discharges, and sets up inZ a current that equals that resulting from the the circuit is closed at e. Thus such inductioncoils serve to neutralize of the static charge, and prevent any false pulsation on the main line resulting from the return static charge acting in m.

It will be apparent that the closing of the keye and the connecting of the battery Z2 with the line tends to set up in the line and to earth currents of opposite polarity to those resulting fromthe battery c, because the positive of the one and the negative of the other are to the ground and line, respectively, and this local circuit (c a 3 e b) serves to maintain an unbroken connection, that offers but little resistance to the pulsation from the distant ceived, ing sent or not.

I claim as my invention-q The battery a Z1 in a local circuit, connected to the line, in which is a circuit-breaker, a nger-key, in combination with the magnet Z m, branch 71 and resistance 7c, and the induction-coils fg, the parts operating substantially as set forth.

Signed by me this 19th day of August, A..

' THOS. A. EDISON. Witnesses:

GHAs. H. SMTTH, GEO. T. PINOKNEY.

or balance the effect 

